This type of sensor is distinguished by the presence of a voltage and ground wire connection to the sensor. The sensor contains an internal resistor. The change in resistance of the internal circuit results in a change of voltage that is detected by the electronic control module. Typically this type of sensor is used to measure temperature of machine fluids. Common examples of the analog, passive sensor include the Torque Converter Oil Temperature Sensor, the Hydraulic Oil Temperature Sensor, or the Air Conditioner Evaporator Coil Temperature Sensor. (For troubleshooting purposes a chart relating temperature to resistance should be included for analyzing temperature sensors.)
The following is a list of codes that are associated with the passive (analog) circuits of the machine.
| Transmission ECM (MID 81) | ||
|---|---|---|
| DTC | Code Description | System Response |
| 177-3 | Transmission Oil Temperature Sensor: Voltage Above Normal | When this diagnostic code occurs, there is no change in the system operation.
Some transmission calibrations are disabled. |
| 177-4 | Transmission Oil Temperature Sensor: Voltage Below Normal | When this diagnostic code occurs, there is no change in the system operation.
Some transmission calibrations are disabled. |
| 826-3 | Torque Converter Oil Temperature Sensor: Voltage Above Normal | When this diagnostic code occurs, there is no change in the system operation.
The torque converter outlet oil temperature gage is disabled. |
| 826-4 | Torque Converter Oil Temperature Sensor: Voltage Below Normal | When this diagnostic code occurs, there is no change in the system operation.
The torque converter outlet oil temperature gage is disabled. |
Possible causes for an FMI 3 diagnostic code are:
- The return circuit is open.
- The signal circuit is open or the sensor is disconnected.
- The signal circuit is shorted to another circuit.
- The sensor has failed.
- The ECM has failed. This condition is unlikely.
Possible causes for an FMI 4 diagnostic code are:
- The signal circuit for the sensor is shorted to ground.
- The sensor has failed.
- The ECM has failed. A failure of the ECM is unlikely.
| |
| Illustration 1 | g03651746 |
|
Schematic of the J1 Transmission ECM Passive/Analog Sensors | |
Note: The diagram above is a simplified schematic of the System Voltage connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. For the complete schematic, refer to the latest revision of: Electrical Schematic, UENR4996, "844K Wheel Dozer (T4F) Electrical System Schematic".Electrical Schematic, UENR1697, "844K Wheel Dozer (LRC) Electrical System Schematic"
The table below is a reference that can be used when checking the resistance of the temperature sensors listed in the table above.
| CELSIUS TEMPERATURE | FAHRENHEIT TEMPERATURE | EQUIVALENT RESISTANCE |
|---|---|---|
| 0° | 32° | 3268.3 Ω |
| 10° | 50° | 1991.4 Ω |
| 20° | 68° | 1249.5 Ω |
| 30° | 86° | 805.5 Ω |
| 40 ° | 104° | 532.3 Ω |
| 50° | 122° | 360 Ω |
| 60 ° | 140° | 248.7 Ω |
| 70° | 158° | 175.2 Ω |
| 80° | 176° | 125.7 Ω |
| 90° | 194° | 91.7 Ω |
| 100° | 212° | 68 Ω |
| 110° | 230° | 51.2 Ω |
| 120° | 248° | 39 Ω |
This type of sensor is distinguished by the presence of a voltage and ground wire connection to the sensor. The sensor contains an internal resistor. The change in resistance of the internal circuit results in a change of voltage that is detected by the electronic control module. Typically this type of sensor is used to measure temperature of machine fluids. Common examples of the analog, passive sensor include the Torque Converter Oil Temperature Sensor, the Hydraulic Oil Temperature Sensor, or the Air Conditioner Evaporator Coil Temperature Sensor. (For troubleshooting purposes a chart relating temperature to resistance should be included for analyzing temperature sensors.)
The following is a list of codes that are associated with the passive (analog) circuits of the machine.
| Implement ECM (MID 82) | ||
|---|---|---|
| DTC | Code Description | System Response |
| 600-3 | Hydraulic Oil Temperature Sensor: Voltage Above Normal | Activates when the voltage is > 4.975 VDC. Electrohydraulic demand fan will be at max speed. The events related to this sensor signal are disabled. Implement Filter Bypass warnings are disabled. |
| 600-4 | Hydraulic Oil Temperature Sensor: Voltage Below Normal | Activates when the voltage is < 0.363 VDC. Electrohydraulic demand fan will be at max speed. The events related to this sensor signal are disabled. Implement Filter Bypass warnings are disabled. |
| 779-3 | Cab Air Temperature Sensor: Voltage Above Normal | The Auto Temperature Control feature is disabled. |
| 779-4 | Cab Air Temperature Sensor: Voltage Below Normal | The Auto Temperature Control feature is disabled. |
| 2357-3 | Air Conditioner Evaporator Coil Temperature Sensor: Voltage Above Normal | Air conditioning is disabled. |
| 2357-4 | Air Conditioner Evaporator Coil Temperature Sensor: Voltage Below Normal | Air conditioning is disabled. |
| 2663-3 | Cab Ventilation Duct Temperature Sensor: Voltage Above Normal | The Auto Temperature Control feature is disabled. |
| 2663-4 | Cab Ventilation Duct Temperature Sensor: Voltage Below Normal | The Auto Temperature Control feature is disabled. |
Possible causes for an FMI 3 diagnostic code are:
- The return circuit is open.
- The signal circuit is open or the sensor is disconnected.
- The signal circuit is shorted to another circuit.
- The sensor has failed.
- The ECM has failed. This condition is unlikely.
Possible causes for an FMI 4 diagnostic code are:
- The signal circuit for the sensor is shorted to ground.
- The sensor has failed.
- The ECM has failed. A failure of the ECM is unlikely.
| |
| Illustration 2 | g03651752 |
|
Schematic of the J1 Implement ECM Passive/Analog Sensors | |
Note: The diagram above is a simplified schematic of the System Voltage connections. The schematic is electrically correct. However, not all the possible harness connectors are shown. For the complete schematic, refer to the latest revision of: Electrical Schematic, UENR4996, "844K Wheel Dozer (T4F) Electrical System Schematic".Electrical Schematic, UENR1697, "844K Wheel Dozer (LRC) Electrical System Schematic"
The table below is a reference that can be used when checking the resistance of the temperature sensors listed in the table above.
| Chart for 376-7257 Pressure Switch Gp and 308-2525 Temperature Sensor Gp | ||
|---|---|---|
| CELSIUS TEMPERATURE | FAHRENHEIT TEMPERATURE | EQUIVALENT RESISTANCE |
| 0° | 32° | 3268.3 Ω |
| 10° | 50° | 1991.4 Ω |
| 20° | 68° | 1249.5 Ω |
| 30° | 86° | 805.5 Ω |
| 40° | 104° | 532.3 Ω |
| 50° | 122° | 360 Ω |
| 60° | 140° | 248.7 Ω |
| 70° | 158° | 175.2 Ω |
| 80° | 176° | 125.7 Ω |
| 90° | 194° | 91.7 Ω |
| 100° | 212° | 68 Ω |
| 110° | 230° | 51.2 Ω |
| 120° | 248° | 39 Ω |
Diagnostic Trouble Code Procedure
Note: Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure and in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.
| Troubleshooting Test Steps | Values | Results |
|---|---|---|
| 1. Identify The Active DTC Code Associated With The Suspect Circuit | Codes present. |
FMI 3 diagnostic code, proceed to Test Step 2. FMI 4 diagnostic code, proceed to Test Step 5. |
| Begin Process For FMI 3 Troubleshooting HERE | ||
| 2. Check For An Open In The Signal Circuit A. Turn the key start switch and the disconnect switch to the OFF position. B. Disconnect the J1 ECM connector. C. At the machine harness connector for the sensor, attach a jumper wire between the sensor contacts. D. At the J1 ECM machine harness connector, measure the resistance from Sensor Signal Contact to Sensor Return Contact. |
The resistance measurement is less than 5 Ω. |
OK - The resistance measurement is less than 5 Ω. Proceed to Test Step 3. NOT OK - The resistance measurement is greater than 5 Ω. There is an open in the machine harness in the sensor return circuit. Repair: Repair or replace the harness. STOP |
| 3. Check For An Open In The Sensor Circuit A. The key start switch and disconnect switch remain in the OFF position. B. The harness connector remains disconnected from the sensor. C. Disconnect the J1 and J2 connectors from the ECM. D. At the harness connector for the sensor, install a jumper wire. E. At the harness connector for the ECM measure the resistance at the contacts for the sensor. |
The resistance reading is less than 5 Ω. |
OK - The resistance is less than 5 Ω. Proceed to Test Step 4. NOT OK - The resistance is greater than 5 Ω. There is an open in the machine harness somewhere between the ECM and sensor in the sensor supply circuit. Repair: Repair or replace the harness. STOP |
| 4. Check The Signal Circuit For A Short A. The disconnect switch and the key start switch remain in the OFF position. B. The "J1" ECM connector remains disconnected. C. Disconnect the "J2" machine harness connector from the ECM. D. Remove the jumper wire that was installed for the previous step at the machine harness connector for the sensor between contacts 1 and 2. E. At the "J1" and "J2" harness connectors for the ECM, measure the resistance between the sensor contact and all "J1" and "J2" contacts. |
Each resistance reading is greater than 5K Ω. |
OK - Each resistance measurement is greater than 5KΩ. The sensor may have failed. Repair: Replace the sensor. NOT OK Any resistance measurement less than 5K Ω. There is a short in the machine harness somewhere between the sensor signal circuit wire and the circuit with the low-resistance measurement. Repair: Repair the harness or replace the harness. STOP |
| Begin Process For FMI 4 Troubleshooting HERE | ||
| 5. Check The Sensor A. Turn key start switch and disconnect switch ON. B. Ensure that the diagnostic code is active. C. Disconnect sensor from machine harness. |
DTC remains active. |
OK - Diagnostic code remains active and does not change. Proceed to Test Step 6. NOT OK - The diagnostic code changes from an FMI 4 to an FMI 3. The sensor has failed. Repair: Replace the sensor. STOP |
| 6. Check The Wiring Harness Of The Sensor For A Short To Ground A. Turn the key start switch and the disconnect switch OFF. B. Disconnect machine harness connection at the sensor. C. Disconnect machine harness connections from the ECM. D. At the machine harness connector for the switch panel, measure the resistance from the signal contact of machine harness to all possible sources of ground. Measure resistance to all contacts of machine harness connectors for the ECM. |
Each reading greater than 5K Ω. |
OK - All resistance readings are greater than 5K Ω. Proceed to Test Step 7. NOT OK - One or more of the readings are less than 5 Ω. Repair: A short exists between the signal contact and the circuit with the low resistance. Repair or replace the machine harness. Note: A resistance greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is greater than 5K Ω would indicate an open in the circuit. STOP |
| 7. Check If The Diagnostic Code Remains A. Turn the key start switch and the disconnect switch ON. B. Clear all diagnostic codes. C. Operate the machine. D. Stop the machine and engage safety lock lever. E. Check if diagnostic code for the sensor is active. |
DTC Code is no longer active. |
OK - Diagnostic code does not exist. Initial diagnostic code may have been caused by poor electrical connection or short at one of the harness connections. Resume machine operation. Repair: The initial diagnostic code was probably caused by a poor electrical connection or a short at one of the harness connectors. Resume normal machine operation. STOP NOT OK - Diagnostic trouble code has not been corrected. Repair: If the diagnostic code has not been corrected after performing the procedure a second time, follow the procedure below for replacing the ECM. Prior to replacing the ECM, always contact the Technical Communicator at your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, see Troubleshooting, "ECM - Replace". STOP |